Spring adjustment for firearms



May 16, 1961 G. WILHELM 2,984,037 SPRING ADJUSTMENT FOR FIREARMS Filed Feb. 6, 195s g JNVENToR /Is Afrox/ve vs.

Patented May 16, 1961 2,984,037 SPRING ADJUSTMENT FOR FIREARMS Gary Wilhelm, New Haven, Conn., assignor to The High Standard Manufacturing Corporation, Hamden, Conn., a corporation of Connecticut Filed Feb. 6, 1959, Ser. No. 791,599

'5 Claims. (Cl. 42-69) This invention relates to ring mechanisms for tirearms, and it relates more particularly to means for adjusting the sear spring in a firearm in order to vary the thrust required to pull the trigger when tiring the gun.

An object of the present invention is to provide means for adjusting the trigger pull, which is the force required to overcome the resistance to movement of the trigger when the firing mechanism is cocked. Another object of the invention is to arrange the scar-spring adjusting means such that the desired adjustment can be made without disassembling the gun. A further object of the invention is to provide a trigger adjusting device which is mechanically and structurally simple in order to avoid malfunctioning, as well as to render such device inexpensive to manufacture. A specific object of one aspect of the invention is to provide an adjusting screw for the sear spring wherein accidental rotation of the screw is prevented by a spring-detent arrangement which provides distinctly audible clicks as the adjusting screw is rotated.

With the above objects in view and some others which will be apparent to those skilled in the art from the descriptions hereinafter, a trigger adjusting device embodying the invention comprises a frame on which the firing member, such as a pivoted hammer for example, and a sear are supported, the sear being movable into and out of cocking engagement with the firing member. A sear spring resiliently urges the Sear into cocking engagement with the hammer, and Sear-spring adjusting means mounted in a passage through said frame engage said sear spring so as to increase or decrease the pressure exerted by the Sear spring on the Sear, said searspring adjusting means including a screw threaded in the outer end of said passage through said frame where it is accessible for adjustment from the outside of the gun, rendering it unnecessary to disassemble the gun in order to make the desired adjustment. By increasing or decreasing the, pressure exerted by the sear spring on the sear, the amount of force required to move the sear out of the sear notch or shoulder on the hammer or other firing member is increased or decreased, and therefore the trigger pull, which is the sum of all the forces resisting movement at the trigger including friction, will be varied proportionately.

In order to prevent accidental rotation of the adjusting screw due to vibration or shock to which a firearm is subjected when tired, the present invention contemplates employment of a novel detent arrangement for the searspring adjusitng screw, in which the sear spring provides the resilient force required for the detent action. To this end, the adjusting means includes an elongated plunger guided in the frame of the gun for longitudinal movement only, with its outer end engaging the adjusting screw and its inner end engaging the sear spring. Complementary cam surfaces are formed on the engaging portions of the plunger and adjusting screw, respectively, with such surfaces normally positioned in matching relation with each other whereby,

upon rotation of said screw relative to the plunger by a predetermined amount, the plunger is cammed inwardly by the interengaging cam surfaces on the plunger and adjusting screw, depressing the sear spring. As the adjusting screw is rotated further the camming surfaces are again brought into matching relation and the plunger is snapped back into full engagement with the adjusting screw. Consequently, in order to rotate the adjusting screw, it is necessary to cam the sear spring inwardly, making it virtually impossible to accidentally change the adjustment of the scar spring. However, a desired adjustment can be easily made by means of a screw driver or similar tool Without disassembling the gun. Each increment of rotation of the adjusting screw, which may be for example half a turn of the screw, is distinctly noticeable from the clicks produced by the plunger as it is snapped back into full engagement with the adjusting screw. This action can also be felt as the screw is rotated. The amount by which the screw is rotated is therefore easily determined by counting the clicks as the adjustment is made.

`Certain particularly desirable embodiments of the invention are illustrated in the accompanying drawings, in which Fig. l is a side elevational view, partly broken away and partly in cross-section, of a semi-automatic pistol incorporating the invention;

Fig. 2 is an exploded view of parts of the firing mechanism shown in perspective; and

Fig. 3 shows a modification of the scar-spring adjusting device.

The firing mechanism of the semi-automatic pistol of the so-called blow-back type shown in the drawings for illustrative purposes consists of a firing pin 10 longitudinally movable in a slide 12 which reciprocates longitudinally on the frame 14 in a Well known manner. Firing pin 10 is urged rearwardly by a spring 11 so that its rear end normally projects slightly rearward of a vertical wall 16 inside slide 12 in position where it can be struck by a pivoted hammer 18 in order to fire a cartridge (not shown) positioned within the chamber of barrel 20 mounted forwardly of slide 12 and against which slide 12 is forced by a return spring (also not shown).

Hammer 18 is pivoted on a pin 22 supported at both ends in frame 14 and is operated by a hammer spring 24 located in the grip portion of frame 14 on a hammer strut 26 which at its upper end is pressed by means of spring 24 against pin 2S mounted in hammer 18 in a more or less conventional manner. The upper end of hammer strut 26 fits into a deep slot 30 (Fig. 2) provided in the under edge of hammer 1S and through which pin 23 extends. A sear 32 is pivoted rearwardly of hammer 18 on a pin 34 supported in frame 14. The Sear nose 36 of sear 32 extends downwardly and slightly forwardly into a scar notch 38 in the cylindrically shaped rear edge 39 of hammer 18 with the forward tip 40 of poor trigger action. Moreover, when the hammer falls to the broken line position shown in Fig. l, the full force of hammer spring 24 is applied as the hammer strikes t-he firing pin 10.

The scar nose 35 of sear 32 is urged forwardly by a scar spring 44 into engagement with the rear edge 39 of hammer 18 so that the front edge of sear nose 36 engages the hammer adjacent the upper corner of sear notch 38 and the tip 40 of sear 32 projects slightly into Sear notch 38 into the path of the lower corner 42 thereof. Accord I ingly, when the hammer is pivoted back (clockwise as shown) somewhat beyond its full-line position as seen in Fig. 1 during the rearward stroke of slide 12, the nose of Sear 32 will project into Sear notch. 38 and, on the` forwardz stroke of yslide 12, the Sear notch corner 42,'w engages the under edge or Sear surface of sear nose 40 sothatfurther movement of the hammer is arrested. A sear bar 46M extending longitudinally of the frame and actually located outside of the side wall of frame 14, which has been removed in Fig. 1 in order to show the firingY mechanism, is illustrated in its relative position with respect to the other parts of the gun. Sear bar 46 connectsthe trigger 48 with the upper end of sear 32 so that when the trigger is pulled, sear 32vwill be rotated counterelockwise as shown in Fig. l in order to release hammer 1,8 and tire the gun. To this end, sear bar 46 is pivoted at its forward end to the upper end of trigger 48, which in turn is pivoted about the trigger pivot pin S0. Adjacent its opposite or rear end, sear bar 46 is provided with an upwardly facing notch 52 which receives a lug 54 on the upper end of scar 32. A scar bar spring (not shown) exerts an upwardly and rearwardly directed force against the front edge of a finger portion 56 on the underside of sear bar 46 in order to resiliently urge notch 52 into engagement with 1ug754 on sear 32, while at the same time to urge sear bar 46 longitudinally to the rear. The rearward component of this action will pivot trigger 48 in a clockwise direction asy viewed in Fig. l in order to return trigger 48 to its normal position, or to maintain it in that position whenever sear bar 46 is disconnected from sear 32.

Provision for disconnecting the sear from the trigger is of course essential in a semi-automatic firearm of the type here shown in order that the gun will not either misfre or re fully automatic as in a machine gun, if the trigger is `held in its retracted position. For this purpose, a -hump 58 is provided on the upper edge of sear bar 46.' which is depressed by the slide 12 immediately after a cartridge is fired, thereby dropping the notch S2 out of engagement with lug 54 on Sear 32 so that the sear can swing back under the urge of sear spring 44 into Y position for engagement with Sear notch 38' as soon as the hammer is returned to cocked position. Sear bar 46 is positively prevented from lifting into engagement with scar lug 54 until slide 12 returns to battery position and the trigger 48 is released so that the sear bar can move longitudinally rearward under the urge of the aforesaid sear-bar spring.

A quick-acting barrel takedown device 60 located in the forward portion of frame 14 above the trigger-guard is provided for the purpose ofV disassembling barrel from the frame. This consists of a locking pin 62 which is rigidly secured in the barrell and extends into interlocking engagement with a spring-loaded plunger 64. Since this device forms no part of the present invention, no further explanation of it is believed necessary in the present disclosure. A rear sight 66 is provided on the upper edge of barrel 20. It will also be noted that the usual safety notch 68 is formed in the rear surface 39 of hammer 18l in order to prevent release of the hammer in ease the sear 32 malfunctions and does not properly engage with sear notch 38,

'In the preferred embodiment of the invention shown in Figs. l and 2., the sear spring 44 is of the torsion type, being formed in this instance of wire doubled over and bentso as to form forward arm-portion 70 having-a Sear-engaging loop 72 at its upper end. Double coils 74 are formed at the lower end of arm-portion 70 by eoiling each of the two lengths of wire outwardly from the center. A mounting pin 76 extendsthroughfcoils 74 and is ixed in the opposite side wallsof frame 14.

Extending upwardly and rearwardly of coil 74 is the tail i portion 7S of spring 44, which is formed by bending the twov llengthsfof wire inwardly until they meet and then upwardly in side-by-side relation. The upper end 80 of tail portion 78 is bent rearwardly and then upwardly again to t in a slot 82 at the inner end of a plunger 84. Plunger 84 is supported for longitudinal movement in a passage 86 (lFig. 1) which extends completely through the rear end 88 of frame 14 and opens onto the outer face thereof. The rear or outer part 90 of passage 86Y is internally threaded in order to receive an adjusting screw 92, which is capable of moving plunger 84 inwardlyy against sear spring 44 to increase the pressure exerted by spring 44against sear 32.

As may be seen best in Fig. 2, the rear or outer end of plunger 84is provided with a V-shaped nose portion 94 which is received in matching relation by a correspondingly shaped recess 96 in the front end of adjusting screw 92. Since plunger 82 is prevented from rotating by interengagement of the end portion 80 of sear spring 444 in the slot 82, rotation of adjusting screw 92 in either direction causes plunger 84 to move forwardly against sear spring 44 as the complementary cam surfaces of nose portion 94 and recess 96 move out of matching relation with each other. In the particular arrangement here shown, after a quarter turn of adjusting screw 92, the tip of the V-shaped nose portion 94 on plunger 84 extends transversely across recess 96 of adjusting screw 92. A further quarter turn of adjusting screw 92 brings the cam surfaces of portions 94 and 96 back into matching relation.

When adjustment of the sear spring is made, the adjusting screw 92 is usually turned comparatively rapidly with the aid of a screw driver in one-half revolution steps, `with ythe result that the plunger 84 is moved back and forth in its passage 86 and, with each step, snaps backrinto Vmatching relation in which portions 94 and 96 are fully engaged. This provides a distinct Vclicking sound, as well as unmistakable feel in the adjusting screw, thereby facilitating adjustment and also preventing accidental rotation of the adjusting screw once the desired adjustment has been attained. It is obvious that rotation of adjusting screw 92 causes it to move longitudinally in the threaded portion 90 of passage 86, thereby increasing or decreasing the force exerted by sear spring 44 on sear'32, depending on the direction in which screw 92 is turned. At Vthe same time, sear spring 44 is intermittently depressed by the camming action between the adjusting screw 92 and plunger 84, which action however has no effect on the adjustment of the spring since plunger 84 will always be returned to full matching engagement with screw 92 under the urge of the sear spring 44.

In the particular iirearm shown in the drawing and speciiically described hereinabove, it was desired to provide a trigger pull which could be varied from two pounds,rwhich is considered to be a fairlyv light, to a pull of three pounds. In other Words, by setting the adjusting screw 92 at its rearmost position in passage 90, tail portion 78 of sear spring 44 is at its most retracted position so that the force exerted on sear 32 by the sear spring is at a predetermined minimum providing -a trigger pull of about two pounds. When the adjusting screw is turned down as, far forwardly as it will go, the Sear spring is further loaded, producing a trigger pull of approximately three pounds. Since the trigger pull is determined by all the forces resisting rearward movement of the trigger, including those produced by the trigger spring and friction, the Sear spring pressure of course constitutes only'part of the trigger pull. In this instance less than half the total trigger pull is attributable to the pressure of the Sear spring when the Sear-spring adjustment is set for minimum trigger pull. On the other hand, when the scar spring is fully loaded in order to provide maximum trigger pull, the sear spring isV responsible for more than two-thirds of the load. 1 Y

Fig. 3 shows a modified form of Sear-spring adjustment, in which the grasshopper type sear spring hereinabove described is` replaced by a coil spring`v 44 located inthe passage 86 through the rear end of frame 14. An adjusting screw 92 with a plain front face bears against the outer end of spring 44 compressing it inwardly against a plunger 100, which is guided in the inner portion of passage 86 and projects into engagement with the rear surface of the sear nose 36 of sear 32. Plunger 100 is provided with an enlarged ball 102 which bears against sear 32. It will be noted that in this arrangement, as in the one previously described, the scar spring can be adjusted in order to provide a fairly wide range of trigger pull by simply turning adjusting screw 92 with a screw driver or other suitable tool from outside the gun. Consequently, there is no need for the shooter to disassemble the gun in order to adjust the trigger pull.

It will be apparent from the foregoing disclosure of certain embodiments of the present invention that the spring-detent arrangement of the spring-adjusting means is applicable not only for adjusting the sear spring, but also for adjusting similar operating springs for firearms.

What is claimed is:

l. In a tiring mechanism for member and a sear member movable into and out of cocking position with respect to said iiring member, the combination comprising a frame on which said members are supported, a sear spring resiliently urging said sear member into cocking position, and scar-Spring adjusting means mounted in a substantially straight passage through said frame, said adjusting means engaging said sear spring for varying the pressure exerted by said sear spring on said sear member; said scar-spring adjusting means comprising an adjustable screw threaded within said passage and located Vadjacent the outer end thereo an elongated plunger lguided in said passage inwardly of and coaxially with said adjusting screw for longitudinal movement therein with its outer end engaging said screw and its inner end engaging said sear spring, said plunger being forced inwardly against said sear spring by said adjusting screw, and anti-rotation means for preventing rotation of said plunger in said passage, the engaging ends of said plunger and adjusting screw having complementary cam surfaces normally in registry with each other so that said surfaces are in full engagement with each other, said cam surfaces being so formed with respect to the axis of rotation of said adjusting screw that upon a predetermined increment of rotation of said screw said cam surfaces are moved out of registry with each other causing said plunger to be shifted longitudinally against said Sear spring and, upon further rotation of said adjusting screw,

firearms having a tiring said cam surfaces are brought into registry again whereby said plunger is shifted longitudinally, under the urge of said sear spring, back into full surface engagement with said vadjusting screw.

2. 'Ihe combination defined in claim 1, wherein said cam surfaces are formed by a V-shaped nose portion on the outer end of said plunger and a correspondingly shaped recess on the inner end of said screw, said nose portion being received within said recess when in matching relation with each other.

3. The combination deiined in claim 2, wherein said anti-rotation means comprises a transverse slot formed on the inner end of said plunger, and said Sear spring comprises a torsion spring supported on said frame and having one end engaging said sear while the other end is retained in said slot on the inner end of said plunger.

4. A spring-tension adjusting device for firearms comprising in combination a frame, an operating spring mounted on said frame, said frame having a substantially straight passage extending completely through a portion thereof in the direction of said operating spring, an elongated plunger guided in said passage and projecting from one end thereof into spring for compressing the same, said plunger being movable longitudinally within said passage, an adjusting screw threaded within the opposite and of said passage and engaging the end of said plunger coaxially therewith, said plunger being forced against said operating spring by said adjusting screw, and anti-rotation means for preventing rotation of said plunger in said passage; the engaging ends of said plunger and said adjusting screw, respectively, having complementary cam surfaces normally in registry with each other so that said surfaces are in full engagement with each other, said cam surfaces being so formed with respect to the axis of rotation of said adjusting screw that upon a predetermined increment of rotation of said screw said cam surfaces are moved out of registry with each other causing said plunger to be shifted longitudinally against said operating spring and, upon further rotation of s aid adjusting screw, said cam surfaces are brought into registry again whereby said plunger is shifted longitudinally, under the urge of said operating spring, back into full surface engagement with said adjusting screw,

5.- The combination defined in claim 4, wherein said anti-rotation means comprises a transverse slot formed on the end of said plunger which engages said operating spring, said operating spring comprising a torsion spring having one of its free ends retained in said plunger slot.

References Cited in the file of this patent UNITED STATES PATENTS 2,249,232 Smith July 15, 1941 2,474,456 Barnett June 28, 1949 FOREIGN PATENTS 209,660 Switzerland July 16, 1940 engagement with said operatingV 

